Research On Optimal Scheduling Control Of Active Power For Offshore Wind Farm

As the wind power technology advanced,many countries,especially those have mature technology,have begun exploring offshore wind resource for its abundant amount.There are large scale wind power was integrated effectively and the crisis of energy and environment has been alleviated,however,the stability of the grid was affected.At present there are many challenges for C hina in this area,such as deficiencies in the utilization of wind power and the difficulty in long distance transmission of wind power,furthermore,the enterprises related cannot achieve good economic benefits just rely on the way of traditional large-power generation directly.Based on the current situation of wind power development and the related policies,this thesis focuses on optimizing the schedule process of active power of offshore wind farm to maintain the stability of power system,to promote the integration of wind power and to construct grid-friendly offshore wind farm.The main work of this thesis are summarized as follows:(1)By introducing the doubly-fed induction generator(DFIG)power system,the control process of the active power of the power system is studied,and then this thesis puts forward the optimal dispatching control system of offshore wind farm.The purpose of this control system is to optimize the allocation of active reference output of each unit in the wind farm following the dispatching instruction,then the power characteristics of DFIG and the relevant knowledge of multi-agent are introduced as the theoretical basis for the design of control algorithm.(2)The frequency stability of the grid reflects the balance between the generation and the load demand,The maximum power of the wind farm is maintained when the demand is large,to increase the grid power generation as far as possible,the difference supplied by other generators or storage device.Otherwise,the power generation of wind turbine is limited,the turbine work in load shedding operation.In this thesis,a sequential optimal control strategy is proposed.Firstly,the units are divided into three categories,such as critical output type,low wind speed type and high wind speed type,according to the operate condition and power characteristics of the wind turbine.Secondly,choosing the stability of the system and the response speed of the frequency as the criterion to control the three types turbines adjust according to the demand in order.Finally,the control strategy is verified based on the MATLAB simulation platform.(3)There are differences exist between different DFIG of the wind farm in the power generation capacity in actual operation,when the difference is large,the traditional incremental consistency control will lead to the deviation between the active power output and the scheduling instruction.For this reason,this thesis proposes a distributed coordinated contro l scheme based on ratio consensus algorithm to assigning the active reference output of the wind speed type and high wind speed type units,and to optimize the frequency control of the wind farm.Compared with the centralized control algorithm,the stability and flexibility of the algorithm proposed are greatly improved.The multi-agent simulation model is built in MATLAB/SIMULINK,and the corresponding simulation analysis is carried out to verify the rationality and the validity of the method proposed.